1. Field of the Invention
The present invention relates generally to electrical apparatus which is designed to operate when energized or powered from either of two different sources of electrical energy, each of which supplies energy of a character or form which is radically different from that of the energy supplied by the other of the sources. Such apparatus is often referred to as dual or two-way powered apparatus. Specifically, the invention relates to apparatus of the noted type which has the capability of being connected to and powered by either a low voltage direct current or DC energy source, such as a battery, or a high voltage alternating current or AC energy source, such as the usual AC supply or distribution system. More specifically, the present invention relates to apparatus as just defined which includes a portion or component requiring low voltage DC energy to energize or power it, and which furnishes such energy to said portion when the apparatus is connected to either of the noted DC and AC sources.
As used herein, the term low voltage DC energy or low voltage DC means energy at a DC voltage which is relatively low with respect to the voltage of the usual AC system, and which may be of the order of 6 to 30 volts. Similarly, the term high voltage AC energy or high voltage AC, as used herein, means energy at an AC voltage which is relatively high with respect to the above-defined low DC voltage, and which is usually of the order of 120 or 240 volts.
2. Description of the Prior Art
Dual powered apparatus of the type noted above, which can be energized or powered by connecting it either to a low voltage DC source, such as a battery, or to an AC system, is known in the art. Examples of such known apparatus are the numerous available radio and television receivers, tape recorders, testing apparatus, and similar equipment which can be powered either by being connected to an external battery, such as that contained in an external battery pack or that employed in an automotive vehicle, or by being plugged into a receptacle of an AC system.
Each of the arrangements of the type just described with which I am familiar requires and effectively includes two sets or pairs of input or energizing terminals. One of these pairs of terminals is provided for connecting the apparatus to the AC system, and the other pair of these terminals is provided for connecting the apparatus to the battery or other DC energy source. Each of these pairs of terminals is so internally connected to the circuitry of the apparatus that the terminals of the pair must be connected only to the designated type of energy source, and must not be connected to the type of source for which the other pair of terminals is provided. Although each of these pairs of terminals is usually associated with the type of conductor or cord set which is normally associated only with the corresponding type of energy source, care must still be exercised to prevent either pair of terminals from inadvertently being connected to the wrong type of energy source. For example, if the low voltage DC input terminals are inadvertently connected to the AC system, tripped circuit breakers, blown fuses, and/or damage to the equipment are likely to result. Therefore, the presence of two sets of input terminals in the known arrangements, and the need for connecting each set of terminals only to its designated energy source, amount to undesirable characteristics or shortcomings of those arrangements.
Moreover, each arrangement of the last-noted type requires some form of mechanical or electrical interlock device to afford the needed protection in the event that both sets of input terminals are connected to their respective energy sources simultaneously. This is especially true where the apparatus is utilized with an associated external battery pack. Such interlock devices necessarily add to the complexity and cost of the apparatus and are a potential source of problems. They thus constitute a further shortcoming of the known apparatus.
It is also known in the art to provide arrangements which, when connected to a high volume AC energy source, utilize semiconductor switches and adjustable RC triggering circuits to furnish variable voltage AC or DC energy to high voltage AC or DC load devices, such as lamps and motors. Arrangements of this type are used extensively as lamp dimmers and motor speed controllers. Examples of these and other similar arrangements are the arrangements which are illustrated throughout Chapters 9 and 10 (Pages 173 through 223) of the General Electric Silicon Controlled Rectifier Manual, 4th edition, published in 1967. However, none of the known arrangements of this type of which I am aware is arranged or used to furnish effectively the same low voltage DC energy to a low voltage DC device when energized through a single set of input terminals from either a low voltage DC energy source or a high voltage AC energy source.